Force and Laws of Motion Part 3: MCQs (Q51–Q75)
⚡ Force and Laws of Motion – Class 9 Science MCQs
Section 3: Newton’s Third Law & Applications (Q51–Q75)
Q51. Newton’s third law states:
A. Force = mass × acceleration
B. Every action has an equal and opposite reaction
C. Force is rate of change of momentum
D. An object continues in state of rest or uniform motion
✅ Correct Answer: B. Every action has an equal and opposite reaction
Explanation:
- A. Second law.
- B. Correct, action = reaction.
- C. Second law.
- D. First law.
Q52. The recoil of a gun is an example of:
A. Newton’s first law
B. Newton’s second law
C. Newton’s third law
D. Conservation of energy
✅ Correct Answer: C. Newton’s third law
Explanation:
- C. Correct, bullet moves forward (action), gun recoils backward (reaction).
Q53. A person walking on ground is able to move forward due to:
A. Inertia
B. Friction
C. Action-reaction pair
D. Momentum
✅ Correct Answer: C. Action-reaction pair
Explanation:
- Person pushes ground backward (action), ground pushes forward (reaction).
Q54. Swimming is possible due to:
A. Law of inertia
B. Law of gravitation
C. Newton’s third law
D. Conservation of momentum
✅ Correct Answer: C. Newton’s third law
Explanation:
- Swimmer pushes water backward → water pushes swimmer forward.
Q55. A rocket moves upward by expelling gases downward. This illustrates:
A. Newton’s first law
B. Newton’s second law
C. Newton’s third law
D. Conservation of mass
✅ Correct Answer: C. Newton’s third law
Q56. If we press a wall with force, the wall:
A. Applies no force
B. Applies equal opposite force
C. Applies greater force
D. Breaks always
✅ Correct Answer: B. Applies equal opposite force
Explanation:
- Action = pressing, reaction = equal opposite push.
Q57. Jumping of a person from boat to shore makes boat move backwards due to:
A. Conservation of momentum
B. Newton’s third law
C. Newton’s first law
D. Inertia
✅ Correct Answer: B. Newton’s third law
Explanation:
- Person jumps forward (action), boat pushed backward (reaction).
Q58. When birds fly, they push air downward with wings. The reaction is:
A. Air pushes them forward
B. Air pushes them upward
C. Air does nothing
D. Gravity helps
✅ Correct Answer: B. Air pushes them upward
Q59. Which is NOT an example of Newton’s third law?
A. Recoil of gun
B. Jumping from boat
C. Ball hitting wall and rebounding
D. Object at rest on table
✅ Correct Answer: D. Object at rest on table
Explanation:
- Resting object = balance of forces, not action-reaction.
Q60. The action and reaction forces:
A. Act on same body
B. Act on different bodies
C. Cancel each other always
D. Are unequal
✅ Correct Answer: B. Act on different bodies
Explanation:
- That’s why they don’t cancel out in motion.
Q61. A man is pushed backward when firing a gun because of:
A. Momentum of bullet
B. Conservation of energy
C. Newton’s third law
D. Work done
✅ Correct Answer: C. Newton’s third law
Q62. While jumping from a height, a man bends his knees. This is to:
A. Increase time of impact
B. Decrease time of impact
C. Reduce momentum
D. Increase acceleration
✅ Correct Answer: A. Increase time of impact
Explanation:
- Increased time → reduces force (F = Δp/Δt).
Q63. Action-reaction forces:
A. Are equal and opposite
B. Act on same body
C. Cancel each other in all cases
D. Are not related
✅ Correct Answer: A. Are equal and opposite
Q64. Which of these explains why we are able to walk?
A. Newton’s first law
B. Newton’s second law
C. Newton’s third law
D. None
✅ Correct Answer: C. Newton’s third law
Explanation:
- Feet push ground backward → ground pushes us forward.
Q65. A book lying on table experiences reaction force from:
A. Gravity
B. Table
C. Air
D. None
✅ Correct Answer: B. Table
Explanation:
- Action = book’s weight downward, reaction = normal force upward.
Q66. Why does a boat move backward when a person jumps from it?
A. Newton’s first law
B. Newton’s second law
C. Newton’s third law
D. Inertia
✅ Correct Answer: C. Newton’s third law
Q67. Walking is an example of Newton’s third law because:
A. We push Earth backward, Earth pushes us forward
B. Earth pulls us downward
C. We pull Earth upward
D. Gravity pulls us forward
✅ Correct Answer: A. We push Earth backward, Earth pushes us forward
Q68. An inflated balloon moves forward when air is released. Which law?
A. Newton’s first law
B. Newton’s second law
C. Newton’s third law
D. Law of gravitation
✅ Correct Answer: C. Newton’s third law
Q69. If a body exerts a force on another, the second body:
A. Exerts no force
B. Exerts greater force
C. Exerts equal opposite force
D. Stops motion
✅ Correct Answer: C. Exerts equal opposite force
Q70. When a man jumps from boat to shore, momentum of system (man + boat):
A. Increases
B. Decreases
C. Remains conserved
D. Becomes zero
✅ Correct Answer: C. Remains conserved
Q71. A horse pulls cart forward by:
A. Overcoming cart’s inertia
B. Pushing ground backward
C. Pulling cart directly
D. Reducing cart’s weight
✅ Correct Answer: B. Pushing ground backward
Explanation:
- Horse pushes ground backward → ground pushes horse forward.
Q72. Why does a rocket rise up?
A. It pushes Earth downward
B. Expelled gases push it upward
C. Heat lifts it
D. Gravity decreases
✅ Correct Answer: B. Expelled gases push it upward
Q73. When hammer strikes a nail, nail exerts force back on hammer. This is:
A. Newton’s first law
B. Newton’s second law
C. Newton’s third law
D. Inertia
✅ Correct Answer: C. Newton’s third law
Q74. Why does a fish swim forward in water?
A. Water pushes fish backward
B. Fish pushes water backward
C. Fish pushes water backward, water pushes fish forward
D. Gravity helps
✅ Correct Answer: C. Fish pushes water backward, water pushes fish forward
Q75. In action-reaction pair:
A. Both forces act on same body
B. Both forces act on different bodies
C. Both cancel each other completely
D. Both unequal in magnitude
✅ Correct Answer: B. Both forces act on different bodies
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